What is ATA Carnet?

Legal Definition
Jointly administered by the World Customs Organization (WCO) and the International Chamber of Commerce through its World Chambers Federation, the ATA Carnet is an international customs document that permits the tax-free and duty-free temporary export and import of goods for up to one year. The Carnet eliminates the need to purchase temporary import bonds. So long as the goods are re-exported within the allotted time frame, no duties or taxes are due. Failure to re-export all or some of the goods listed on the Carnet results in the payment of applicable duties and taxes. Failure to remit those duties results in a claim from the foreign customs service to the importer's home country.

The acronym ATA is a combination of French and English terms "Admission Temporaire/Temporary Admission."

In 2012, over 175 000 Carnets were issued internationally for goods valued at over US$ 20 billion. In 2014, 178,150 Carnets were issued with a total value exceeding US$ 30.5 billion.
-- Wikipedia
Legal Definition
A document for duty free imports. No bond is posted for the duty charged. It is used for literature, samples, designs, machinery, and demonstration equipment. The chambers of commerce issue it and pay the duty . AKA a temporary admission.